JP7840193B2 - Liquefied gas tank - Google Patents

Description

This disclosure relates to a liquefied gas tank for storing liquefied gas.

Liquefied gas tanks, which store liquefied gases such as liquefied hydrogen and liquefied natural gas, are equipped with pumps to discharge the liquefied gas from the tank. When discharging the liquefied gas through the tank roof, the pump is located inside the tank, and the liquefied gas is sent to the outside through a cylindrical pump barrel that penetrates the tank roof.

In this case, for example, the pump may need to be removed from the tank for maintenance. Patent Document 1 discloses a pump lifting device for lifting the pump through its pump barrel during such work. This pump lifting device comprises a work deck constructed on the upper surface of the tank roof, a vertically extending column member fixed to the work deck, and a winch fixed to the column member and connected to the pump via a wire.

Japanese Patent Publication No. 2017-132619

According to the pump lifting device described in Patent Document 1, the pump can be removed from the tank through the pump barrel by winding a wire using a winch. However, because it is necessary to construct structures such as a work deck and column members on the tank roof to support the winch, there is a problem that the device tends to become complex or large.

This disclosure is made in view of the circumstances described above, and aims to provide a liquefied gas tank that enables the removal of the pump from inside the tank with a relatively simple configuration.

To solve the aforementioned problems, a liquefied gas tank according to one aspect of this disclosure comprises a tank body for storing liquefied gas, a pump disposed within the tank body for discharging the liquefied gas, a pump barrel including a cylindrical portion housing the pump and extending upward from the pump's housing position to the outside of the tank body, and an upper housing chamber located above the cylindrical portion and defining a space capable of receiving the pump, a lifting device disposed within the upper housing chamber for lifting the pump into the upper housing chamber through the cylindrical portion, and an on/off valve provided between the cylindrical portion and the upper housing chamber so as to be openable and closable.

The liquefied gas tank described in this disclosure allows for the removal of the pump from inside the tank with a simple configuration.

This is a schematic diagram showing the structure of a liquefied gas tank according to one embodiment of the present disclosure. This is a partially enlarged view of Figure 1, showing details of the pump barrel and its surrounding structure. This is a diagram illustrating the procedure for removing the pump. This is a diagram illustrating the procedure for installing a pump. This figure illustrates a modified example of the above embodiment.

The liquefied gas tank according to the embodiments of this disclosure will be described in detail below with reference to the drawings. The liquefied gas tank of this disclosure is a tank for storing low-temperature liquefied gases. The stored liquefied gases include, for example, liquefied hydrogen, liquid helium, liquid nitrogen, liquefied ammonia, liquefied natural gas, or liquefied petroleum gas. In particular, the liquefied gas tank according to this disclosure is suitable as a tank for storing liquefied hydrogen.

[Overall structure of the tank]
Figure 1 is a schematic diagram showing the structure of a liquefied gas tank 1 according to one embodiment of the present disclosure. The liquefied gas tank 1 is a tank for storing cryogenic liquefied hydrogen LH, and is a flat-bottomed tank with a multi-shell structure that is installed on the ground. The liquefied gas tank 1 comprises a tank body 10, a pump barrel 2, a pump 3, a lifting device 4, an on-off valve 5, and a gas replacement device 6. The tank body 10 is a dome-shaped container for storing liquefied hydrogen LH. The pump 3 is a submersible pump positioned inside the tank body 10 while immersed in liquefied hydrogen LH. The pump barrel 2 is a cylindrical body extending vertically through which the liquefied hydrogen LH discharged from the tank body 10 by the pump 3 flows. The lifting device 4 is a device for lifting the pump 3 through the pump barrel 2 when necessary for maintenance, etc. The on-off valve 5 is a valve that can be opened and closed in the middle of the pump barrel 2. The gas replacement device 6 is a device for replacing the gas in the space above the on-off valve 5 in the pump barrel 2 (the upper storage chamber 22, which will be described later).

The tank body 10 is a sealed body that defines a space for storing liquefied hydrogen (LH) internally. While Figure 1 simplifies the tank body 10 to show a single-shell structure, the actual tank body 10 has a multi-shell structure, such as a double-shell or triple-shell structure. In the case of a double-shell structure, the tank body 10 consists of an outer tank erected on a foundation and an inner tank enclosed within the outer tank. The liquefied hydrogen (LH) is stored inside the inner tank. A thermal insulation layer is formed between the outer tank and the inner tank, and this thermal insulation layer is filled with a powdered insulating material, such as granular perlite, and a low-boiling-point gas. In the case of a triple-shell structure, the tank body 10 has an intermediate tank between the outer tank and the inner tank.

Figure 2 is a partially enlarged view of Figure 1, showing details of the pump barrel 2 and its surrounding structure. As shown in Figures 1 and 2, the pump barrel 2 penetrates the tank roof 11, connecting the inside and outside of the tank body 10. That is, the pump barrel 2 is formed to extend vertically, penetrating the tank roof 11, from a height near the bottom of the tank body 10 to a height above the tank roof 11. The pump barrel 2 functions as a discharge pipe for discharging liquefied hydrogen LH from the tank body 10 to the outside.

The pump barrel 2 comprises a cylindrical portion 21 located below the on-off valve 5 and an upper housing chamber 22 located above the on-off valve 5. In other words, the pump barrel 2 is divided into the cylindrical portion 21 and the upper housing chamber 22 by the on-off valve 5, which is installed midway along its vertical direction.

The cylindrical portion 21 is a straight cylindrical body with a substantially constant cross-section in the vertical direction. It extends upward from a position corresponding to the pump 3 inside the tank body 10 to the outside of the tank body 10 (above the tank roof 11). The cylindrical portion 21 has a lower end portion 21a that houses the pump 3 and an upper end portion 21b that protrudes above the tank roof 11. A discharge port 24 is provided protruding from the upper end portion 21b. The discharge port 24 is a port for discharging liquefied hydrogen L discharged when the pump 3 is operating to the outside.

The upper storage chamber 22 is connected to the upper end 21b of the cylindrical portion 21 via an on-off valve 5. The upper storage chamber 22 includes a storage chamber body 26 with an open top surface and a head plate 25 that covers the top opening of the storage chamber body 26. The head plate 25 corresponds to the ceiling member in this disclosure.

The containment chamber body 26 is a stepped cylindrical member formed such that the cross-sectional area of the upper part is larger than the cross-sectional area of the lower part. Specifically, as shown in Figure 2, the containment chamber body 26 has a small-diameter portion 26a connected to the on-off valve 5, a large-diameter portion 26b with a larger inner diameter than the small-diameter portion 26a, and an intermediate portion 26c connecting the small-diameter portion 26a and the large-diameter portion 26b. The intermediate portion 26c is formed such that its inner diameter increases towards the upper part closer to the large-diameter portion 26b.

The head plate 25 is a plate-shaped member that constitutes the ceiling of the upper storage chamber 22. The head plate 25 is detachably attached to the upper end of the storage chamber body 26 (large-diameter section 26b) via bolts or the like, so as to open and close the upper opening of the storage chamber body 26. A hanging handle 25a is provided protruding from the upper surface of the head plate 25.

The pump 3 is housed in the lower end 21a of the pump barrel 2 (cylindrical portion 21) and positioned within the tank body 10, immersed in liquefied hydrogen L. A foot valve 23 is attached to the lower end 21a of the pump barrel 2 to open and close the intake port, which is its lower opening. The pump 3 is mounted on the foot valve 23, and the weight of the pump 3 causes the foot valve 23 to descend, opening the intake port of the pump barrel 2. When the pump 3 is driven with the intake port open in this manner, it draws in liquefied hydrogen LH from the tank body 10 through the intake port, pumps it upward, and discharges the liquefied hydrogen LH to the outside through the pump barrel 2 (cylindrical portion 21).

The lifting device 4 is located inside the upper housing chamber 22 of the pump barrel 2. The lifting device 4 is a winch capable of lifting the pump 3, which is housed in the lower end portion 21a of the pump barrel 2 (cylindrical portion 21), up to the upper housing chamber 22. Specifically, the lifting device 4 comprises a drum 41 that is rotatable around a horizontal axis and a lifting wire 42 that connects the drum 41 and the pump 3. The lifting wire 42 is wound around the drum 41 and is routed to extend downward from the drum 41 to the pump 3. The drum 41 is a drum that can rotate in the forward direction to wind up the lifting wire 42 and in the reverse direction to pull out the lifting wire 42, and is supported by a support member 43 fixed to the lower surface of the head plate 25. That is, the drum 41 is rotatably supported inside the upper housing chamber 22 by being attached to the lower surface of the head plate 25 via the support member 43. Furthermore, the lifting device 4 may further include a drive source for rotating the drum 41 in both forward and reverse directions. As the drive source, an appropriate type may be used, such as a pneumatic type using gas or an electric type using electricity.

The on-off valve 5 is an openable and closable valve positioned between the cylindrical section 21 and the upper storage chamber 22, and can be switched between an open state that connects the cylindrical section 21 and the upper storage chamber 22 and a closed state that blocks them from each other. In the figures, a symbol representing a valve that is blacked out indicates that the valve is closed, and a symbol representing a valve that is not blacked out indicates that the valve is open. As shown in Figures 1 and 2, the on-off valve 5 is kept open during operation of the liquefied gas tank 1. The suspension wire 42 is routed through the open on-off valve 5 and extends from the upper storage chamber 22 to the cylindrical section 21, connecting the pump 3 at the lower end 21a of the cylindrical section 21 and the drum 41 in the upper storage chamber 22. On the other hand, when the pump 3 is removed from the tank body 10 for maintenance or other purposes, the pump 3 is lifted from the cylindrical section 21 to the upper storage chamber 22 by the lifting device 4. At this time, the on-off valve 5 is kept open until the pump 3 has completed its movement into the upper housing chamber 22, and is then switched to the closed state. To allow the pump 3 to move between the cylindrical section 21 and the upper housing chamber 22, the on-off valve 5 has a valve body that allows the pump 3 to pass through when open. A ball valve with a hollow ball-shaped valve body is preferred as such an on-off valve 5.

The gas replacement device 6 is a device that replaces the gas in the upper storage chamber 22 when necessary, such as when the pump 3 is withdrawn, and comprises a hydrogen gas supply source 61, a nitrogen gas supply source 62, a first inlet pipe 63, a second inlet pipe 64, a first outlet pipe 65, a second outlet pipe 66, and first to fourth valves 67A to 67D. The hydrogen gas supply source 61 is a supply source that supplies gas corresponding to the liquefied gas (in this case, liquefied hydrogen LH) stored in the tank body 10, i.e., hydrogen gas, and includes, for example, a pneumatic pump capable of pumping hydrogen gas. The nitrogen gas supply source 62 is a supply source that supplies nitrogen gas as an inert gas, and includes, for example, a pneumatic pump capable of pumping nitrogen gas. The first inlet pipe 63 is a pipe that connects the hydrogen gas supply source 61 and the upper storage chamber 22. The second inlet pipe 64 is a pipe that connects the nitrogen gas supply source 62 and the upper storage chamber 22. The first outlet pipe 65 and the second outlet pipe 66 are pipes connected to the upper containment chamber 22 for discharging the gas to be replaced from the upper containment chamber 22. The first valve 67A is a valve that can be opened and closed on the first inlet pipe 63, the second valve 67B is a valve that can be opened and closed on the second inlet pipe 64, the third valve 67C is a valve that can be opened and closed on the first outlet pipe 65, and the fourth valve 67D is a valve that can be opened and closed on the second outlet pipe 66.

The gas replacement device 6 replaces the gas in the upper storage chamber 22 by operating with the on-off valve 5 closed, that is, when communication between the cylindrical section 21 and the upper storage chamber 22 is blocked. Specifically, the gas replacement device 6 can fill the upper storage chamber 22 with hydrogen gas supplied from the hydrogen gas supply source 61, or with nitrogen gas supplied from the nitrogen gas supply source 62. In other words, the upper storage chamber 22 can be switched between being filled with hydrogen gas and being filled with nitrogen gas. During gas replacement to change the gas in the upper storage chamber 22, the first to fourth valves 67A to 67D are opened as needed. On the other hand, during operation of the liquefied gas tank 1, as shown in Figures 1 and 2, the first to fourth valves 67A to 67D are all kept closed.

[Pump removal work]
As mentioned above, the pump 3 may be removed from the tank body 10, for example, for maintenance. The details of this procedure will be explained using Figure 3.

Prior to the removal of pump 3 (Figure 3), the first step is to push the liquefied hydrogen LH in the pump barrel 2 into the tank body 10. During operation of the liquefied gas tank 1, liquefied hydrogen LH is present inside the pump barrel 2. Generally, except when discharging liquefied hydrogen LH, the liquefied hydrogen LH in the pump barrel 2 is present up to the same height as the liquid level in the tank body 10. From the viewpoint of reducing the lifting resistance of pump 3 or suppressing liquid entrapment, it is desirable that there is no liquid in the pump barrel 2 when pump 3 is removed. Therefore, in this embodiment, as preparation before removing pump 3, a gas corresponding to the stored liquefied gas (in this case, liquefied hydrogen LH), i.e., hydrogen gas, is supplied to the pump barrel 2 from the discharge port 24. At this time, the first to fourth valves 67A to 67D are all kept closed. Then, the liquefied hydrogen LH in the pump barrel 2 is pushed back into the tank body 10 by the hydrogen gas supplied from the discharge port 24. This results in the pump barrel 2 being completely filled with hydrogen gas. Note that this extrusion of liquefied hydrogen (LH) can be performed only as needed and can be omitted.

Next, as shown in step 1-1 of Figure 3, the pump 3 is lifted to the upper containment chamber 22 using the lifting device 4. During this lifting, the on-off valve 5 remains open, just as it is during operation of the liquefied gas tank 1. The lifted pump 3 passes through the open on-off valve 5 and moves from the cylindrical portion 21 of the pump barrel 2 to the upper containment chamber 22. Furthermore, the first to fourth valves 67A to 67D are all kept closed until the movement (lifting) of the pump 3 to the upper containment chamber 22 is complete. This ensures that the upper containment chamber 22 remains filled with hydrogen gas until the movement (lifting) of the pump 3 is complete.

Next, as shown in step 1-2 of Figure 3, the gas in the upper containment chamber 22 is replaced from hydrogen gas to nitrogen gas. Specifically, the on-off valve 5 is switched from the open state to the closed state, and the second valve 67B and the third valve 67C are switched from the closed state to the open state. Meanwhile, the first valve 67A and the fourth valve 67D are kept closed. This blocks communication between the upper containment chamber 22 and the cylindrical section 21, allowing nitrogen gas to be introduced into the upper containment chamber 22 from the second inlet pipe 64. The introduced nitrogen gas fills the upper containment chamber 22, pushing the hydrogen gas present in the upper containment chamber 22 out through the first outlet pipe 65. That is, the state of the upper containment chamber 22 is switched from being filled with hydrogen gas to being filled with nitrogen gas. The hydrogen gas pushed out through the first outlet pipe 65 is, for example, recovered in a predetermined recovery device connected to the first outlet pipe 65.

Next, as shown in step 1-3 of Figure 3, the head plate 25 is removed from the upper storage chamber 22, and the lifting device 4 and pump 3 are transported out together with the head plate 25. Specifically, with all of the first to fourth valves 67A to 67D closed, the fixing means such as bolts that secure the head plate 25 to the storage chamber body 26 are released, and the head plate 25 is removed from the storage chamber body 26 and transported out using an external transport device such as a winch that has been prepared in advance. For example, with the wire W extending from the external transport device attached to the lifting handle 25a of the head plate 25, the external transport device is operated to transport the head plate 25 to a predetermined destination. When the head plate 25 is removed by this transport, the top surface of the upper storage chamber 22 (storage chamber body 26) is opened, and the gas (nitrogen gas) inside the upper storage chamber 22 is replaced with air as appropriate. Here, the lifting device 4 is fixed to the head plate 25, and the lifting device 4 holds the pump 3 by a lifting wire 42. Therefore, when the head plate 25 is removed, the lifting device 4 and the pump 3 are also removed along with the head plate 25.

With the above steps completed, the process of removing pump 3 from the tank body 10 is finished. The removed pump 3 will then be subjected to maintenance and other prescribed procedures at the destination.

[Pump installation work]
Next, the process of installing the pump 3 onto the tank body 10 will be explained using Figure 4.

First, the lifting device 4 and pump 3 are inserted into the upper containment chamber 22. This operation is the reverse of steps 1-3 in Figure 3, and is achieved by fixing the head plate 25, which includes the lifting device 4 and pump 3, to the upper surface of the containment chamber body 26. At this time, the on-off valve 5 and the first to fourth valves 67A to 67D are all kept closed. With the head plate 25 fixed in this state, air is trapped inside the upper containment chamber 22.

Next, as shown in step 2-1 of Figure 4, the gas in the upper containment chamber 22 is replaced from air to nitrogen gas. Specifically, while keeping the on-off valve 5, the first valve 67A, and the fourth valve 67D closed, the second valve 67B and the third valve 67C are opened. This allows nitrogen gas to be introduced into the upper containment chamber 22 from the second inlet pipe 64, and air to be discharged from the upper containment chamber 22 through the first outlet pipe 65. In other words, the state in the upper containment chamber 22 is switched from being filled with air to being filled with nitrogen gas.

Next, as shown in step 2-2 of Figure 4, the gas in the upper containment chamber 22 is replaced from nitrogen gas to hydrogen gas. Specifically, while maintaining the on-off valve 5 in the closed state, the first valve 67A and the fourth valve 67D are switched from the closed state to the open state, and the second valve 67B and the third valve 67C are switched from the open state to the closed state. As a result, hydrogen gas is introduced into the upper containment chamber 22 from the first inlet pipe 63, and nitrogen gas is discharged from the upper containment chamber 22 through the second outlet pipe 66. In other words, the state inside the upper containment chamber 22 is switched from being filled with nitrogen gas to being filled with hydrogen gas.

Next, as shown in step 2-3 of Figure 4, the pump 3 is lowered from the upper housing chamber 22 to the lower end 21a of the cylindrical section 21 using the lifting device 4. Before this lowering, the first to fourth valves 67A to 67D are all closed, and the on-off valve 5 is switched from the closed state to the open state. The pump 3 moves from the upper housing chamber 22 to the lower end 21a of the cylindrical section 21, passing through the on-off valve 5, which is in the open state.

As a result, the pump 3 is returned to its proper storage position within the pump barrel 2 (the lower end 21a of the cylindrical portion 21), and the process of installing the pump 3 into the tank body 10 is completed.

[Effects and Effects]
As described above, in this embodiment, a lifting device 4 capable of lifting the pump 3 from the cylindrical portion 21 of the pump barrel 2 to the upper storage chamber 22 is arranged in the upper storage chamber 22, and an on/off valve 5 is arranged between the cylindrical portion 21 and the upper storage chamber 22. This configuration has the advantage that the operation of removing the pump 3 from inside the tank body 10 can be achieved with a relatively simple setup.

In other words, according to the configuration of this embodiment, in which the lifting device 4 and the on-off valve 5 are applied to the pump barrel 2, when removing the pump 3 from the tank body 10 for maintenance, etc., the pump 3 can be moved from the cylindrical portion 21 of the pump barrel 2 to the upper storage chamber 22 by lifting the pump 3 with the on-off valve 5 open using the lifting device 4, and then the pump 3 can be transported out from the upper storage chamber 22. In particular, since the lifting device 4 is located in the upper storage chamber 22 of the pump barrel 2, unlike when the lifting device 4 is located outside the pump barrel 2, it becomes unnecessary to construct a separate structure on the tank roof 11 to support the lifting device 4. In other words, in this embodiment, the removal of the pump 3 from the tank body 10 is made easier, thus reducing the man-hours or costs associated with maintenance of the pump 3.

Furthermore, after lifting the pump 3 to the upper chamber 22, the communication between the upper chamber 22 and the cylindrical section 21 can be blocked by switching the on/off valve 5 from the open state to the closed state. This prevents air from flowing from the upper chamber 22 into the cylindrical section 21, while allowing the head plate 25 to be removed from the upper chamber 22, thus opening the upper chamber 22 and allowing the pump 3 to be easily removed from the upper chamber 22. In other words, in this embodiment, the pump 3 can be easily removed from the tank body 10 while preventing air from entering the tank body 10.

Furthermore, in this embodiment, since the lifting device 4 is attached to the lower surface of the detachable head plate 25 that constitutes the ceiling of the upper storage chamber 22, after lifting the pump 3 to the upper storage chamber 22 using the lifting device 4, the pump 3 can be easily removed from the upper storage chamber 22 together with the head plate 25 by removing the head plate 25 from the storage chamber body 26.

Furthermore, in this embodiment, a gas replacement device 6 capable of filling the upper containment chamber 22 with hydrogen gas or nitrogen gas is applied to the pump barrel 2, thereby preventing improper gas inflow and outflow during the removal and installation of the pump 3.

For example, when removing pump 3, replacing the gas in the upper storage chamber 22 with an inert gas, such as nitrogen gas, before removing pump 3 from the upper storage chamber 22 (see Figure 3) prevents the gas corresponding to the stored liquefied gas (liquefied hydrogen LH), i.e., hydrogen gas, from being dispersed into the atmosphere. On the other hand, when installing pump 3, replacing the gas in the upper storage chamber 22 with hydrogen gas before lowering pump 3 from the upper storage chamber 22 into the cylindrical section 21 (see Figure 4) prevents gases other than hydrogen gas from being mixed into the tank body 10.

[Variations]
While preferred embodiments of the present disclosure have been described above, the disclosure is not limited thereto, and variations such as the following are possible.

In the above embodiment, the lifting device 4 was attached to the lower surface of the head plate 25, which constitutes the ceiling of the upper storage chamber 22. However, the lifting device 4 only needs to be located inside the upper storage chamber 22, and its mounting location is not limited to the head plate 25. For example, the lifting device 4 may be detachably attached to the inner wall of the storage chamber body 26.

In the above embodiment, assuming that the liquefied gas stored in the liquefied gas tank 1 is liquefied hydrogen LH, a gas replacement device 6 capable of replacing the gas in the upper containment chamber 22 of the pump barrel 2 with hydrogen gas or nitrogen gas was applied to the pump barrel 2. However, the gas replacement device only needs to be capable of replacing the gas in the upper containment chamber with a gas corresponding to the liquefied gas or an inert gas, and to that extent, the type of replacement gas can be changed as appropriate.

In the above embodiment, a single on-off valve 5 was provided between the cylindrical portion 21 of the pump barrel 2 and the upper storage chamber 22. However, multiple on-off valves may be provided. For example, a first on-off valve could be attached to the upper end of the cylindrical portion 21, a second on-off valve to the lower end of the upper storage chamber 22, and a short cylindrical intermediate chamber could be provided between the first and second on-off valves. This has the advantage of preventing multiple gas inflows and outflows between the upper storage chamber 22 and the cylindrical portion 21 when gas replacement is performed in the upper storage chamber 22.

Although not specifically mentioned in the above embodiment, when discharging liquefied hydrogen LH from the tank body 10 using the pump 3, the liquid level of liquefied hydrogen LH in the pump barrel 2 may rise above the height of the discharging port 24. In particular, if the head of the pump 3 is sufficiently secured to expedite discharging, the liquefied hydrogen LH may reach the height of the lifting device 4 beyond the on-off valve 5. Figure 5 illustrates a structure that incorporates measures to avoid such a situation. The upper storage chamber 122 shown in this figure has increased vertical dimensions compared to the upper storage chamber 22 in the above embodiment (Figures 1 to 4). Furthermore, an annular orifice 126 is provided inside the upper storage chamber 122. The orifice 126 is provided so as to protrude radially inward from the inner wall of the upper storage chamber 122's intermediate vertical section, dividing the interior of the upper storage chamber 122 into two vertical sections. In other words, the upper chamber 122 has an orifice 126, a first divided chamber 122A formed above the orifice 126, and a second divided chamber 122B formed below the orifice 126. The first divided chamber 122A has space to accommodate the lifting device 4. The second divided chamber 122B has space to receive the pump 3 (shown by a dashed line in Figure 5) which has been lifted above the on-off valve 5 by the lifting device 4.

An opening 126a is formed in the center of the orifice 126, through which the suspension wire 42 can pass. Since the area of the opening 126a is sufficiently smaller than the cross-sectional area of the upper containment chamber 22, a significant flow resistance acts on the liquefied hydrogen LH passing through the opening 126a. This prevents the liquefied hydrogen LH from reaching the lifting device 4 above the orifice 126 during discharge.

In the modified example shown in Figure 5, the orifice 126 needs to be removed from the upper housing chamber 122 to allow the pump 3 to be removed from the upper housing chamber 122. That is, the orifice 126 is detachable from the upper housing chamber 122. Specifically, in the modified example in Figure 5, the upper housing chamber 122 has a two-part structure, with its first divided chamber 122A and second divided chamber 122B connected by flanges. The orifice 126 is attached between flange F1 of the first divided chamber 122A and flange F2 of the second divided chamber 122B via fastening members such as bolts. When removing the pump 3, the orifice 126 can be simultaneously removed from flanges F1 and F2, allowing the pump 3 to be removed from the upper housing chamber 122.

[summary]
The above embodiments and their modified forms can be summarized as follows.

The liquefied gas tank comprises a tank body for storing liquefied gas, a pump positioned within the tank body for discharging the liquefied gas, a pump barrel including a cylindrical section housing the pump and extending upward from its housing position to the outside of the tank body, and an upper housing chamber located above the cylindrical section and defining a space capable of receiving the pump, a lifting device positioned within the upper housing chamber for lifting the pump into the upper housing chamber through the cylindrical section, and an on/off valve provided between the cylindrical section and the upper housing chamber so as to be openable and closable.

According to this embodiment, when removing the pump from the tank body for maintenance or other purposes, the pump can be moved from the cylindrical portion of the pump barrel to the upper storage chamber by lifting it with the on/off valve open using a lifting device, and then the pump can be removed from the upper storage chamber. In particular, since the lifting device is located in the upper storage chamber of the pump barrel, unlike when the lifting device is located outside the pump barrel, it becomes unnecessary to construct a separate structure on the tank roof to support the lifting device. In other words, according to this disclosure, the removal of the pump from the tank body becomes easier, thus reducing the man-hours or costs associated with pump maintenance.

Furthermore, after the pump has been lifted to the upper chamber, the communication between the upper chamber and the cylindrical section can be blocked by switching the on/off valve from the open to the closed position. This prevents air from flowing from the upper chamber into the cylindrical section while allowing the upper chamber to be opened, and the pump to be easily removed from the upper chamber. In other words, according to this disclosure, the pump can be easily removed from the tank body while preventing air from entering the tank body.

Preferably, the upper storage chamber comprises a storage chamber body with an open top and a removable ceiling member covering the top opening of the storage chamber body, and the lifting device is attached to the lower surface of the ceiling member.

In this embodiment, after lifting the pump to the upper housing chamber using a lifting device, the ceiling member can be easily removed from the housing chamber body, allowing the pump to be easily transported out of the upper housing chamber together with the ceiling member.

Preferably, the liquefied gas tank further comprises a gas replacement device capable of switching the contents of the upper storage chamber between a state in which it is filled with a gas corresponding to the stored liquefied gas and a state in which it is filled with an inert gas.

In this configuration, it is possible to prevent improper gas inflow and outflow during pump removal and installation. For example, during pump removal, by replacing the gas in the upper containment chamber with an inert gas before removing the pump from the upper containment chamber, it is possible to prevent the gas corresponding to the stored liquefied gas from being dispersed into the atmosphere. On the other hand, during pump installation, by replacing the gas in the upper containment chamber with a gas corresponding to the liquefied gas before lowering the pump from the upper containment chamber into the cylindrical section, it is possible to prevent a gas different from the gas corresponding to the liquefied gas from being mixed into the tank body.

Preferably, the upper housing chamber has an annular orifice projecting radially inward from the inner wall of its intermediate vertical portion, a first partitioned chamber formed above the orifice for housing the lifting device, and a second partitioned chamber formed below the orifice for receiving the pump.

In this embodiment, since an orifice is provided inside the upper containment chamber, it is possible to prevent the liquid level of the liquefied gas from reaching the height of the lifting device when dispensing the liquefied gas using the pump. Furthermore, the lifting device can be housed in the first division chamber above the orifice, and the pump lifted by the lifting device can be received in the second division chamber below the orifice.

LH: Liquefied Hydrogen (Liquefied Gas)
1. Liquefied gas tank 2. Pump barrel 3. Pump 4. Lifting device 5. On/off valve 6. Gas replacement device 10. Tank body 21. Cylindrical section 22. Upper storage chamber 25. Head plate (ceiling member)
26 Main containment chamber 122 Upper containment chamber 122A First divided chamber 122B Second divided chamber 126 Orifice

Claims (4)

The tank body for storing liquefied hydrogen ,
A pump is placed inside the tank body to discharge the liquefied hydrogen ,
A pump barrel including a cylindrical portion that houses the pump and extends upward from the pump's housing position to the outside of the tank body, and an upper housing chamber located above the cylindrical portion and defining a space capable of receiving the pump,
A lifting device is provided in the upper containment chamber and lifts the pump into the upper containment chamber through the cylindrical portion,
An opening/closing valve is provided between the cylindrical portion and the upper storage chamber so as to be openable and closable ,
The system includes a foot valve that opens and closes the intake port for liquefied hydrogen at the lower end of the cylindrical portion ,
The upper storage chamber is a liquefied gas tank that can be connected to both a hydrogen gas source and a nitrogen gas source. In the liquefied gas tank according to claim 1,
The upper storage chamber comprises a storage chamber body with an open top and a removable ceiling member that covers the top opening of the storage chamber body.
The lifting device is a liquefied gas tank attached to the lower surface of the ceiling member. In the liquefied gas tank according to claim 1 or 2,
A liquefied gas tank further comprising a gas exchange device that includes a hydrogen gas supply source and a nitrogen gas supply source, and is capable of switching between a state in which the interior of the upper containment chamber is filled with hydrogen gas and a state in which it is filled with nitrogen gas. The tank body for storing liquefied gas,
A pump is placed inside the tank body to discharge the liquefied gas,
A pump barrel including a cylindrical portion that houses the pump and extends upward from the pump's housing position to the outside of the tank body, and an upper housing chamber located above the cylindrical portion and defining a space capable of receiving the pump,
A lifting device is provided in the upper containment chamber and lifts the pump into the upper containment chamber through the cylindrical portion,
The system includes an opening/closing valve that is provided to open and close between the cylindrical portion and the upper storage chamber,
A liquefied gas tank having an annular orifice projecting radially inward from the inner wall of its upper intermediate portion, a first divided chamber formed above the orifice and housing the lifting device, and a second divided chamber formed below the orifice and capable of receiving the pump.